Unable to resolve towards 8.8.8.8 sometimes

[Lukass Lappuķe]

Dear all,

When resolving towards 8.8.8.8 from a local wi-fi or a personal hotspot, etc. it sometimes fails.

Responses are received from these Google IP addresses:

74.125.46.10
74.125.112.1
74.125.112.9
74.125.x.x
74.125.z.z
74.125.w.w

But when resolving towards 8.8.8.8 from a server on AWS or DO it always succeeds. 

The responses are received from different Google IP addresses:
172.253.199.4
172.253.1.194
172.217.33.132

Why is it so?

An idea: Does Google give a higher priority for big customers like AWS or DO vs the public...? Or is there a different explanation?

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Additionally:

1. We even made a test subdomain xip.teltel.io which is set up exactly the same way and when resolving that domain towards 8.8.8.8 it works fine every time.

The only difference between sip.teltel.io and xip.teltel.io is the load: 

sip receives our customer's traffic and xip only our test requests.

How can you explain that?

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2. We captured the traffic by performing a tcpdump (tcpdump udp and port 53) and noticed that when Google fails to resolve, our name servers never receive a request from Google.

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3. Here you can test the loops for yourself:
This fails with "sip"  - while true; do dig A 42894078.sip.teltel.io @8.8.8.8; done;
This is OK with "xip"- while true; do dig A 42894078.xip.teltel.io @8.8.8.8; done;

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Please Google, can you help us solve this? It seems quite mysterious to us.

Thanks,

Lukass

[Lu Zhao]

Hi Lukass,

Thanks for reporting this problem. Google public DNS is a free service and gives same priority to external customers. Please check if your query volume exceeds our rate limit. 

https://developers.google.com/speed/public-dns/docs/isp

Best,

Lu